Start off slow and easy. Look for a local park or forest preserve with clearly marked trails. Start with a mile or two, then build up as your confidence, fitness/endurance, and experience increases.
I first started seriously hiking when I was 13 or 14, going on all-day Ranger-led hikes in the Teton National Park. If there's a National Park or State Park near you, check their schedule for activities. Not only do they normally provide a list of exactly what to bring, their hikes are usually geared toward casual hikers, plus you'll learn a lot from the ranger.
As far as gear, start with the Ten Essentials, a daypack, and comfortable high-quality boots. Shop for items that are durable, lightweight, and not too expensive. Then add optional items to your pack as you feel necessary - guide books, camera, journal book, etc.
As your experience and confidence grow, you'll be ready for an overnight, then eventually to full-length backpacking trips. That's when the gear starts to really add up $$-wise, weight becomes critical, and selecting quality items really pays off. Tent, sleeping bag, backpack, cook stove, etc.
Skills. Map and compass/GPS/navigating, firebuilding, outdoor cooking, menu planning, logistics, etc. Practice these things at home ~before~ going to the outdoors.
One thing that's really helped me over the years, every time I go backpacking I make a list of exactly every piece of gear and bit of food I'm taking. At the end of the trip I evaluate the list to see which things I didn't use or need, which things should have been better, which things need replacing, etc. My packing procedure is fine-tuned after 20 years.
Where do you live at? Someone could recommend some beginner-level hiking trails near your home, or perhaps even go with you.
-Bob
